Effectiveness of a Rigid Grate for Excluding Pacific Halibut, Hippoglossus stenolepis, From Groundfish Trawl Catches

ibut bycatch limits are reached and, as a result, substantial quantities of ground­ fish remain unharvested each year. Flatfish fishermen have long been in­ terested in developing gear modifica­ tions to reduce this bycatch and allo w increases in fishing time and harvests. Some have developed their own de­ signs for halibut excluders. 1 Most of these excluders put a size selection panel across the trawl a short distance ahead of the codend. Holes in the panel are large enough to allow smaller target species to pass but will exclude the much larger halibut, which are guided toward an escape slot. The performance of these excluders had not been sci­ entifically evaluated. Although the ad hoc experience of these fishermen con­ vinced some that these excluders were effective in particular fisheries, the need was seen for scientific evaluations of at least one excluder’s selectivity. Costs associated with the intensive catch sam­ pling and experimental design, which were necessary for such evaluations, were well beyond what any single fish­ ing operation could reasonably manage during an open fishery. In 1998, the Groundfish Forum, an organization representing groundfish trawl catcher/processors that fish in Alaska waters, obtained a National Marine Fisheries Service (NMFS) ex­ empted fishing permit to test system­ atically the exclusion of halibut from flatfish trawls with a selected industry device. The work was done in coopera­ tion with NMFS, which provided assis­